Three Smart Boys (1937)

When they overhear Miss Witherspoon, the school superintendent, say that nothing short of an epidemic will allow the school to be closed for a week, the Our Gang conspire to fake illness. They paint spots on their faces and go to the doctor. Unfortunately they don't realize the doctor they've chosen is a veterinarian. The doctor humors them by inviting Buckwheat into the examining room, but when a monkey emerges they assume the doctor's "monkey serum" has transformed their pal.